David Jenkins
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| posted on 10/9/07 at 02:06 PM |
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Bike carbs on x-flow?
Just wondering out loud... what are the costs and issues with fitting bike carbs to a moderately tuned 1660cc crossflow engine?
Which carbs are most suitable?
How much should I expect to pay for a set?
What other things would I have to buy?*
*I can foresee...
A manifold (which I could probably make)
A matching bike fuel pump? (or would the engine's mechanical one work OK?)
Different needles/jets? If needed, what do they cost?
This is just pipe-dreaming at the moment, but it is likely to be my next upgrade (if not too expensive).
cheers,
David
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DarrenW
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| posted on 10/9/07 at 02:16 PM |
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Costs shouldnt be too dissimilar to what i have done for the Pinto.
Boggs Manifold - £190.
Carbs - id guess 60 quid ish.
Air filter - £100 new, cheaper if you are more inventive / lucky with 2nd hand find.
Throttle cable - £20 (Mac#1 cable kit highly recommended).
Bike pump - £20.
New pipe work and filters - guess £20.
Choke cable - may not need one but approx £10.
Bits and bobs - springs, bolts, nuts, etc etc - £30 ish.
Gasket - £not sure - £15??
Ref needles / jets - hasnt cost me anything yet. Dont know if i will need dynojet needles yet. I re-drilled my own jets with 1.6mm drill by hand
(didnt use drill - oversize issue).
That should get you running and then you may need a better set up. Im expecting £60 ish for Boggs to set mine up.
It could be up to £450 or so if you buy most things new or as low as £220 or so if you make manifold and source bits more cheaply and shop around.
Is it worth it - ill let you know if i get the stains out of my pants!!!!! (too much information? )
[Edited on 10/9/07 by DarrenW]
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Pdlewis
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| posted on 10/9/07 at 02:17 PM |
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Leaving the manifold to one side as there are many different routes i paid the following for R1 on a 2L ported pinto:
R1 Carbs £70 delivered
R6 Fuel pump £10 delivered
drills (1.60,1.65,1.7 mm) £1.60
Filters £40
Well worth it over the old 32/36
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auzziejim
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| posted on 10/9/07 at 02:27 PM |
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my total on a pinto comes to
carbs £21 (900 diversion)
inlet £0
pump £11 (zx9r)
filters £40
micro drills £2
cables £3
and it pulled all the way through the rev range. much better than any downdraught and imo better than sidedraught webers
i have seen a few pintos using the mechanical fuel pump so cant see why a x/flow would be any different.
i did go out and try to do this on the cheap so looked for bike carbs that people wernt really looking for i.e everyone and his dog wants r1, blade,
bird etc carbs but when the diversion uses much the same carbs for a fraction of the price i wanst going to follow the crowd and waste my hard earned
so shop around and find some cheap ones
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DarrenW
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| posted on 10/9/07 at 02:27 PM |
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its the little bits and bobs that i found added up. i collected parts over too many months so spread the cost.
I also opted to switch to megajolt before swapping the carbs as this was part of the grand plan.
fatboy Dave could do you a cheaper manifold if you dont mind re-spacing the carbs (not sure if this will cause an issue with dizzy clearance on x-flow
though).
There are a few people on here who can make diy manifolds as well but keep quiet. To me its not one of the easist jobs to make hence going Boggs
route. Worst bit is the time it can take to do a decent job. Jacko's photo archive is an inspiration (and maybe some others).
my advice - dont think too long or you will put yourself off and convince yourself its harder than it is.
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David Jenkins
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| posted on 10/9/07 at 02:37 PM |
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I'm already on Megajolt and the dizzy's gone, so there's lots of space!
If possible, I'd like to get carbs that'll work horizontally (but some people say that it doesn't matter too much). Also I
don't know the size of bike to consider, e.g. for throttle bodies people look for those of 600cc or 750cc bikes, but what's good for
carbs? The general theme seems to be 'big'!
Are there any carbs to avoid? For example, are there any that can't be spaced out to suit the manifold? Or have poor reliability, or difficult
to tune, maintain or get spares for?
But as said above - I should stop asking questions and start shopping!
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DarrenW
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| posted on 10/9/07 at 02:48 PM |
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Ref the angle - i had the same discussion with Boggs. They simply asked if id seen the V8 manifold they made - that apparently worked just fine.
I had my manifold made a fair bit shallower than normal (just enough kick in it for filter to clear side rails) and seems good so far. Bikes rarely
travel upright on level roads with very light throttle.
Sorry no idea ref reliability and availability of spares. i was comferted knowing that few bikes cover huge mileagaes so most sets of carbs are in
great condition. Also most seem to be Japanese and are not known for issues. id be surprised if you will need any spares.
Maybe the only factor is that some might be easier to fit filters too etc. On the ZZR1100's its important to get the trumpets and fitting plate
(others will be similar) whereas others ive seen seem to have 4 seperate straight trumpets that will take easy to get sock filters. Personally i
wouldnt fit socks from what ive read. Im happy with my challeger air box but would have searched for a sausage filter otherwise (pipercross, ITG
etc)
Maybe dynojet kits become difficult to source for some carbs, however ive not heard of many people needing one of these.
i forgot you were on megajolt already. Oops. Maybe another factor then is the TPS. Some have one fitted as standard but as ive now sussed out it is
possible to retro fit a pot type TPS to other types as well.
I know someone with a set of ZX9 carbs in garage but cannot get a price off him. I believe these have the TPS.
[Edited on 10/9/07 by DarrenW]
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UncleFista
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| posted on 10/9/07 at 03:28 PM |
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We got our crossflow running on bike carbs, just in time to convert to Zetec ;( but we made another manifold to suit the Zetec.
£10 Mild steel for manifold, 6mm plate and 1mm sheet (to weld into tubes).
£15 CBR600 carbs (ebay 99p plus P+P)
£20 Silicon hose (dunno exactly how much, I already had some)
£15 CBR600 fuel pump (Facet SS carb pump was too high pressure)
£3 Universal throttle cable
£2 for a 1.65 and 1.7mm drill bit
£10 to modify the Megajolt to TPS from MAP
I've not touched the mixture screws or syncronised the carbs but they run better than I ever got my 32/36DGV to run, perfect idle, no flat spots
etc.
Definitely recommended by me 
We had a run out to the coast yesterday and the fuel economy seems to be better than it was with the Weber, I can't be certain, but we
didn't run out of petrol on the way back like we did last time
[Edited on 10/9/07 by UncleFista]
Tony Bond / UncleFista
Love is like a snowmobile, speeding across the frozen tundra.
Which suddenly flips, pinning you underneath.
At night the ice-weasels come...
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David Jenkins
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| posted on 10/9/07 at 03:39 PM |
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I'm confused! 
Darren's using carbs from an ZZR1100, UncleFista's using CBR600 carbs, auzziejim's using 900 Diversion carbs, and pdlewis is using
R1 carbs!
And you all say they're working well for each of you!
Help!!!
(3 exclamation marks - a sure sign of a disturbed mind...)
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UncleFista
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| posted on 10/9/07 at 03:47 PM |
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TBH I think it just goes to show how much easier bike carbs are to get running "right" than twin 40's etc..
I just used carbs from a bike which had a similar horsepower output as I was hoping for in the crossflow, 105bhp, and they had to be cheap, obviously
 .
The Zetec isn't much more than that (115) and runs great, but if I was converting to a 2l I'd probably go with some a bit bigger.
Dunno whether it was just luck it worked out well though
[Edited on 10/9/07 by UncleFista]
Tony Bond / UncleFista
Love is like a snowmobile, speeding across the frozen tundra.
Which suddenly flips, pinning you underneath.
At night the ice-weasels come...
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David Jenkins
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| posted on 10/9/07 at 03:52 PM |
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An almost totally uninformed guess* would suggest that the CBR600 carbs would be good on my ~100BHP x-flow... matching the BHP sounds like a worthy
technique.
I'll get looking, methinks...
*Apart from this discussion, of course!
[Edited on 10/9/07 by David Jenkins]
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DarrenW
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| posted on 10/9/07 at 03:56 PM |
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Comparing the donor bikes doesnt really reflect on what carbs they are i guess. It is quite possible that the carbs are all very similar (im no expert
though). There is probs a big crossover where they can all be OK, but maybe the smaller ones can be restrictive of more power is required. Again pure
guess.
At a guess id say anything from 600 to 900cc bike should be Ok for x-flow. Id probs go for ZX9 or similar on tuned x-flow.
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GaryM
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| posted on 10/9/07 at 05:36 PM |
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David
My winter upgrade project will be to swap to a set of bike carbs on my Xflow (1600 GT with fast road cam). I also plan to install a megajolt,
initially with MAP (so I can test it with my DGV fitted) and then TPS when I fit the bike carbs.
I bought a set of FZR600 carbs because Robocog has already successfully used these on a Pinto upgrade so I knew they could be respaced. They have a
TPS attached and they seem to be cheap (mine cost less than £20 inc p&p).
I'm not sure what to do about the manifold. Carbs slipping out of silicone hose joiners seems to be a recurrent posting so either bracketing the
carbs to the manifold or using the OEM rubbers so they can be bolted to a flange on the manifold (like the weber twin DCOE manfolds) might be a good
solution.
Keep in touch so we can pool knowledge?
Cheers
Gary
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DarrenW
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| posted on 10/9/07 at 05:43 PM |
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Gary you can fit megajolt with TPS at first no probs. I did this with 38DGAS carb and just ran it in 2D mode - better than dizzy. Further improvements
when i get tPS connected hopefully.
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David Jenkins
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| posted on 10/9/07 at 06:48 PM |
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Sort-of drifting off topic (but it's my thread, so nyah-nyah!)
Am I right in thinking that a steel inlet manifold could be brazed or silver-soldered? Both techniques require a mechanically strong joint anyway, so
vibration shouldn't be a major issue, and neither will melt until red-hot. If the inlet manifold gets that hot a collapsing manifold is the
least of your worries! 
Doing it this way would mean that distortion would be negligible (if any at all) and it would be easily within the capabilities of a home mechanic.
MIG welding such a manifold would be quite intricate, with some tricky corners - not impossible, but hard to do tidily.
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jacko
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| posted on 10/9/07 at 08:02 PM |
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quote:
Originally posted by David Jenkins
Sort-of drifting off topic (but it's my thread, so nyah-nyah!)
Am I right in thinking that a steel inlet manifold could be brazed or silver-soldered? Both techniques require a mechanically strong joint anyway, so
vibration shouldn't be a major issue, and neither will melt until red-hot. If the inlet manifold gets that hot a collapsing manifold is the
least of your worries!
Doing it this way would mean that distortion would be negligible (if any at all) and it would be easily within the capabilities of a home mechanic.
MIG welding such a manifold would be quite intricate, with some tricky corners - not impossible, but hard to do tidily.
Hi David have a look in my photo archives under zx9r carbs i made my manifold
Jacko
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David Jenkins
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| posted on 10/9/07 at 08:19 PM |
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quote:
Originally posted by jacko
Hi David have a look in my photo archives under zx9r carbs i made my manifold
Jacko
Yes - I saw your pictures earlier - that's what started me thinking about brazing the whole assembly, rather than welding.
It looks like a good model to follow if I don't re-space the carbs. Did you fabricate the bends, or did you start with straight tube and make
your own shapes?
Oops! Just had another look - fabricated! (nice work)
[Edited on 10/9/07 by David Jenkins]
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David Jenkins
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| posted on 13/9/07 at 07:23 AM |
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Jacko,
I've had a good look at your photos again - very useful. I was wondering how the pipes could be formed and aligned, then I saw your manifold
jig. Very neat.
I've just bought a set of CBR600 carbs off the bay of e, so look forward to many more questions!
cheers,
David
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DarrenW
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| posted on 13/9/07 at 08:13 AM |
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Well done on the carbs David. Do they have TPS fitted. If not i may have some ideas. Todays job for me is fitting TPS to my ZZR's.
What size is the OD of the inlet, i assume you will need some joining pipe so might as well start the search for you Ive got some 48mm ID that might
get you away.
Ive often wondered what would stop someone using an old alloy manifold as a starting point and weld on some new tubes......... (apart from the obvious
specialist welding gear and skills of course)..........
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David Jenkins
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| posted on 13/9/07 at 08:21 AM |
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Not sure about the TPS yet - it wasn't stated in the ad.
However, I was planning to make the manifold with a vacuum take-off on each tube. These will go to a small reservoir then on to my current MAP sensor.
Other people have done this, and apparently it works OK.
I don't know the size of the tube either! Awaiting delivery...
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Pdlewis
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| posted on 13/9/07 at 08:43 AM |
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If the pipe is the same as the stuff you sent to me darren it is top stuff done the job really well on 40mm carbs been on about a month and seems to
be ok with fuel and after a few teething problems (i would suggest to do with the muppet who was fitting them!!) work as treat
I didnt expect the upgrade to make as much difference as it has the sound of 4 individual pots is sweet
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DarrenW
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| posted on 13/9/07 at 10:00 AM |
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That is good news Paul. I still have some of that tube left so will offer a bit to David if it is the right size.
Doh!!! Sorry Dave - forgot you only won them last night so wont have recieved them yet.
i too am very surprised at the difference they have made. Even in 2D ignition mode and maybe not jetted etc correctly the difference is staggering.
Fir point ref using MAP David. I seem to recall some people found it necessary to connect each of the 4 tubes via some sort of damper but dont know
the details, a search may find it but not sure what search string you will need to put in.
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David Jenkins
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| posted on 13/9/07 at 02:01 PM |
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Darren - I'll let you know about the tube - thanks.
I believe that the MAP reservoir can be quite small, just a small can around 4" long, 2" across (or that sort of size, anyway).
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DarrenW
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| posted on 13/9/07 at 02:32 PM |
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Snapper must be running a vacuum connection on his so might be worth a U2U.
http://www.locostbuilders.co.uk/viewthread.php?tid=72201
Not sure where the details are ref the vacuum connection. Didnt someone use an empty compressed air vial used in BB guns???????? I may be way off the
mark but have a vague recollection of it from ages ago.
Can you tell im enjoying helping someone for a change rather than seeking help most of the time
[Edited on 13/9/07 by DarrenW]
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David Jenkins
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| posted on 13/9/07 at 02:57 PM |
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Here's a good discussion on the autosportlabs forum:
LINK
[Edited on 13/9/07 by David Jenkins]
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